// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/posix/file_descriptor_shuffle.h"

#include <ostream>
#include <stddef.h>
#include <unistd.h>

#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"

namespace base {

bool PerformInjectiveMultimapDestructive(
    InjectiveMultimap* m, InjectionDelegate* delegate)
{
    static const size_t kMaxExtraFDs = 16;
    int extra_fds[kMaxExtraFDs];
    unsigned next_extra_fd = 0;

    // DANGER: this function must not allocate or lock.
    // Cannot use STL iterators here, since debug iterators use locks.

    for (size_t i_index = 0; i_index < m->size(); ++i_index) {
        InjectiveMultimap::value_type* i = &(*m)[i_index];
        int temp_fd = -1;

        // We DCHECK the injectiveness of the mapping.
        for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
            InjectiveMultimap::value_type* j = &(*m)[j_index];
            DCHECK(i->dest != j->dest) << "Both fd " << i->source
                                       << " and " << j->source << " map to " << i->dest;
        }

        const bool is_identity = i->source == i->dest;

        for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
            InjectiveMultimap::value_type* j = &(*m)[j_index];
            if (!is_identity && i->dest == j->source) {
                if (temp_fd == -1) {
                    if (!delegate->Duplicate(&temp_fd, i->dest))
                        return false;
                    if (next_extra_fd < kMaxExtraFDs) {
                        extra_fds[next_extra_fd++] = temp_fd;
                    } else {
                        RAW_LOG(ERROR, "PerformInjectiveMultimapDestructive overflowed "
                                       "extra_fds. Leaking file descriptors!");
                    }
                }

                j->source = temp_fd;
                j->close = false;
            }

            if (i->close && i->source == j->dest)
                i->close = false;

            if (i->close && i->source == j->source) {
                i->close = false;
                j->close = true;
            }
        }

        if (!is_identity) {
            if (!delegate->Move(i->source, i->dest))
                return false;
        }

        if (!is_identity && i->close)
            delegate->Close(i->source);
    }

    for (unsigned i = 0; i < next_extra_fd; i++)
        delegate->Close(extra_fds[i]);

    return true;
}

bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
    InjectionDelegate* delegate)
{
    InjectiveMultimap m(m_in);
    return PerformInjectiveMultimapDestructive(&m, delegate);
}

bool FileDescriptorTableInjection::Duplicate(int* result, int fd)
{
    *result = HANDLE_EINTR(dup(fd));
    return *result >= 0;
}

bool FileDescriptorTableInjection::Move(int src, int dest)
{
    return HANDLE_EINTR(dup2(src, dest)) != -1;
}

void FileDescriptorTableInjection::Close(int fd)
{
    int ret = IGNORE_EINTR(close(fd));
    DPCHECK(ret == 0);
}

} // namespace base
